High Concentrations of Organic Contaminants in ... - ACS Publications

Sep 9, 2015 - areas. Ship breaking activities likely act as atmospheric emission sources of PCBs, PAHs, and HCB, thus adding to the .... breaking area...
0 downloads 15 Views 2MB Size
Subscriber access provided by KUNGL TEKNISKA HOGSKOLAN

Article

High concentrations of organic contaminants in air from ship breaking activities in Chittagong, Bangladesh Therese Haugdahl Nøst, Anne Karine Halse, Scott Randall, Anders Borgen, Martin Schlabach, Alak Paul, Atiqur Rahman, and Knut Breivik Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.5b03073 • Publication Date (Web): 09 Sep 2015 Downloaded from http://pubs.acs.org on September 15, 2015

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 36

Environmental Science & Technology

1

High concentrations of organic contaminants in air from ship breaking

2

activities in Chittagong, Bangladesh

3

4

Therese H. Nøst1*, Anne K. Halse2, Scott Randall2,3, Anders R. Borgen2, Martin Schlabach2,

5

Alak Paul4, Atiqur Rahman4,5 and Knut Breivik2,6

6 7 8

1

9

Tromsø, Norway;

NILU-Norwegian Institute for Air Research, FRAM Centre, P.O. Box 6606 Langnes, 9296

10

2

NILU-Norwegian Institute for Air Research, P.O. Box 100, 2027 Kjeller, Norway;

11

3

COWI AS, Division of Environment, Economics and Planning, P.O. Box 123, 1601

12

Fredrikstad, Norway;

13

4

14

Chittagong, Bangladesh;

15

5

16

& Atmospheric Environment, 210044 Nanjing, China;

17

6

University of Chittagong, Department of Geography and Environmental Studies, 4331

Nanjing University of Information Science and Technology, School of Atmospheric Physics

University of Oslo, Department of Chemistry, P.O. Box 1033, 0315 Oslo, Norway.

18 19

*Corresponding author: phone: (+47) 77 75 03 86; fax: (+47) 77 75 03 76; [email protected].

1 ACS Paragon Plus Environment

Environmental Science & Technology

20

Page 2 of 36

Abstract

21 22

The beaches on the coast of Chittagong in Bangladesh are one of the most intense ship

23

breaking areas in the world. The aim of the study was to measure the concentrations of

24

organic contaminants in the air in the city of Chittagong, including the surrounding ship

25

breaking areas using passive air samplers (N=25). The compounds detected in the highest

26

amounts were the polycyclic aromatic hydrocarbons (PAHs) and short-chain chlorinated

27

paraffins (SCCPs), whereas dichlorodiphenyltrichloroethanes (DDTs), hexachlorobenzene

28

(HCB) and polychlorinated biphenyls (PCBs) were several orders of magnitude lower in

29

comparison. PCBs, PAHs and HCB were highest at sites near the ship breaking activities,

30

whereas DDTs and SCCPs were higher in the urban areas. Ship breaking activities likely act

31

as atmospheric emission sources of PCBs, PAHs and HCB thus adding to the international

32

emphasis on responsible recycling of ships. Concentrations of PAHs, PCBs, DDTs, HCB and

33

SCCPs in ambient air in Chittagong are high in comparison to similar studies performed in

34

other parts of Asia. Estimated toxic equivalent quotients (TEQs) indicate elevated human

35

health risks caused by inhalation of PAHs at most sites.

2 ACS Paragon Plus Environment

Page 3 of 36

Environmental Science & Technology

36

Introduction

37

Environmental impacts of hazardous anthropogenic substances is a global concern which has

38

motivated international regulatory initiatives such as the Stockholm1 and Basel Conventions2.

39

Persistent organic pollutants (POPs) and their potential harmful effects to humans and the

40

environment have been researched extensively in industrialized countries, but far less is

41

known about POPs emission sources and environmental concentrations in developing

42

countries. Bangladesh is classified as a Least Developed Country according to the United

43

Nations (UN). In addition, Bangladesh has ratified the Stockholm and the Basel Conventions.

44

Since the 1980's, national environmental regulations have existed in Bangladesh such as the

45

banning of many organochlorine pesticides and polychlorinated biphenyls (PCBs).3 There are

46

several suspected local emission sources of POPs in Bangladesh;3-5 however, there are few

47

studies monitoring concentrations of POPs in the environment in this country, and no studies

48

have been conducted in Chittagong.

49

Chittagong is the second largest city in Bangladesh and has a population of approximately 4.5

50

million people.6 The city hosts a large seaport and extensive industrial activities in and around

51

the city. Ship breaking in Chittagong occurs when ships are dismantled directly on the tidal

52

beaches. This activity began in the 1960's and has since represented a considerable share of

53

the world market of ship breaking.5, 7-10 Out of a total of 1026 ships dismantled globally in

54

2014, 22% of the ships with known scrapping destinations were dismantled in the Chittagong

55

area.11 Concern has arisen regarding these activities and the subsequent emissions of

56

pollutants to the environment.12-14 The materials making up the scrapped ships contain heavy

57

metals and industrial-use POPs like PCBs and polybrominated diphenyl ethers (PBDEs).15 A

58

large fraction of the volume of waste electric and electronic equipment (WEEE) in

59

Bangladesh originates from the ship breaking activities.5, 16 Furthermore, there is no formal

60

management and recycling of obsolete PCB-containing equipment, and this waste is simply 3 ACS Paragon Plus Environment

Environmental Science & Technology

Page 4 of 36

61

deposited in landfills in many areas.3, 5 Burning of such waste could release POPs like PCBs

62

to the air while also generating by-products of combustion such as polycyclic aromatic

63

hydrocarbons (PAHs).17, 18

64

Other potential sources to contaminants in the ambient air in Chittagong area include release

65

and/or generation of unintentionally produced PCBs and PAHs by industrial activities.17-20

66

Also, there are suspected stockpiles and illegal use of pesticides in the area, especially of

67

dichlorodiphenyltrichloroethane (DDT) - which was produced in Chittagong until 1991.3, 4

68

Metal-working lubricants, sealants, plasticizers, and flame retardants are likely widely used in

69

Bangladesh, which may contain short-chain chlorinated paraffins (SCCPs) which can also be

70

considered a pollutant source.21

71

There is limited information on the environmental and human exposure to POPs as a result of

72

ship breaking activities. The objective of this study was to monitor concentrations of PCBs,

73

organochlorine pesticides, PBDEs, SCCPs and PAHs in the air within the urban environment

74

of Chittagong, including a focus on areas with ship breaking activities.

75

4 ACS Paragon Plus Environment

Page 5 of 36

Environmental Science & Technology

76

Materials and methods

77

Sample collection

78

The sampling campaign was conducted in the Chittagong area using passive air samplers

79

(PAS) equipped with polyurethane foam (PUF) disks.22 PAS are regularly used for spatial

80

mapping of pollutants in air monitoring studies on both a regional and global scale.23-27.

81

Detailed descriptions of this sampling method can be found in literature.22, 25, 26, 28 In brief, the

82

PUF disk has a high ability to sorb semi-volatile organic compounds in air and thus

83

accumulate such compounds on the disk during the exposure period. The theoretical amount

84

sorbed on the PUF disk is equivalent to the rate of uptake minus the rate of loss. The initial

85

rate of uptake is linear, but declines as the concentration in the PUF approaches equilibrium.

86

The duration of the linear phase of uptake is dependent on the octanol– air partition

87

coefficient (KOA) of the individual compounds. Thus, compounds that are more volatile (low

88

KOA) will approach equilibrium faster than less volatile compounds (higher KOA).

89

A total of 25 PAS were deployed at 23 different sites in Chittagong and near the ship

90

breaking areas located northwest of the city center in late February 2013 (Supporting

91

Information (SI), Figure S1). The study was performed in parallel to a screening study for

92

concentrations of sulphur dioxide (SO2), nitrogen dioxide (NO2), and ozone (O3) in ambient

93

air of Chittagong.29 Deployment time for the PAS ranged from 7 to 9 days, see SI, Table S1

94

for details. A short deployment time was deliberately selected (i) because high frequencies of

95

detection were anticipated for most analytes, and (ii) to enhance the potential for sampling

96

during the linear uptake phase, reflecting the high temperatures expected during the sampling

97

period in combination with the volatility of the target compounds. The samplers were

98

assembled, deployed, and disassembled by trained personnel from Chittagong University. The

5 ACS Paragon Plus Environment

Environmental Science & Technology

99

Page 6 of 36

sampling campaign also included preparation of field and transport blanks (N=4 and 4,

100

respectively).

101

The research team selected sampling sites in residential, industrial, and background areas as

102

well as in areas in close proximity to ship breaking activities in Chittagong. After the

103

exposure period in the field, the samplers were disassembled and the PUF disks were wrapped

104

in two layers of aluminum foil, placed in sealed plastic bags, and stored in a freezer until

105

analysis.

106

The screening study was performed during the dry season and there was no precipitation

107

recorded during the sampling period. Temperatures during the sampling period were

108

consistently high; 25-30°C high during the day and around 15°C during nighttime. The wind

109

frequency distribution (wind rose) as measured at the Agrabad continuous air monitoring

110

station in Chittagong is presented for the sampling period in SI, Figure S2. The prevailing

111

wind direction in this area was from west-northwest (Bay of Bengal) with wind speeds

112

between 1 and 4 m/s.

113

114

Sample preparation, clean-up and analysis

115

Sample preparation, clean-up and analysis were performed as described in detail by Halse et

116

al.27; only a brief summary along with minor adjustments is provided here. The PUF disks

117

were pre-cleaned using Soxhlet extraction (toluene for 24 hours, acetone for 8 hours, and

118

toluene for additional 8 hours) before deployment. The disks were wrapped in two layers of

119

aluminum foil, placed in sealed plastic bags, and stored in a freezer until shipment. After the

120

exposure period, PUF disks were spiked with internal standards and Soxhlet extracted using

121

n-hexane/10% diethyl ether (8-10 hours, 250 mL). An aliquot (10% volume of extracts) was

6 ACS Paragon Plus Environment

Page 7 of 36

Environmental Science & Technology

122

stored for possible future analysis. The remaining extracts were divided into two identical

123

aliquots for two separate clean-up procedures.

124

One aliquot targeted acid-resistant compounds: PCBs (congeners 28, 52, 101, 118, 138, 153,

125

180), PBDEs (congeners 47, 99), hexachlorocyclohexanes (α-, β- and γ-HCH),

126

dichlorodiphenyltrichloroethanes and one metabolite (DDTs; p,p´-DDT, o,p´-DDT, p,p´-

127

DDE), hexachlorobenzene (HCB), chlordanes (trans-chlordane, cis-chlordane, trans-

128

nonachlor) and SCCPs. This aliquot was treated with concentrated sulfuric acid (2 mL, 2-3

129

times) and further cleaned up using a silica column of activated silica (4 g, preheated 8 hours

130

at 550 °C) and eluted with n-hexane/10 % diethyl ether (30 mL). The other aliquot targeted

131

PAHs (fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene,

132

chrysene/triphenylene, benzo(a)pyrene). As PAHs are acid-labile and difficult to elute from

133

activated silica, a slightly different clean-up method was applied. The solvent was exchanged

134

to cyclohexane before clean up using a deactivated silica column (slurry of 5 g silica

135

deactivated with 8% MilliQ water, and 15 mL cyclohexane) and eluted with cyclohexane (100

136

mL). After clean-up procedures, the extract aliquots were reduced to ~50 µl and added

137

recovery standards.

138

The analyses of PCBs, PBDEs, HCHs, DDTs, and HCB were performed by gas

139

chromatography coupled to a high resolution mass spectrometer (GC-HRMS) in electron

140

impact mode.27 SCCPs and chlordanes were determined by GC-HRMS in an electron capture

141

negative ionization mode and reported as bulk mixture.30 PAHs were analyzed by gas

142

chromatography coupled to a low resolution mass spectrometer (GC-LRMS) in electron

143

impact ionization mode.27

144

145 7 ACS Paragon Plus Environment

Environmental Science & Technology

Page 8 of 36

146

Quality assurance and quality control

147

The analytical procedures were performed according to NS/EN ISO/IEC 17025 accredited

148

routines. A calibration/quantification solution containing all target analytes was analysed

149

along with the samples. Also, analysis of standard reference materials (SRM 1588 and 2206a,

150

National Institute of Standards and Technology) assured low analytical uncertainties of PCBs,

151

PBDEs, HCHs, DDTs, HCB and chlordanes. Further, compounds with a retention time of

152

more than 3 seconds later than corresponding isotope-labeled standards as well as compounds

153

with isomer isotopic ratios deviating >20% from those in the standards were disregarded.

154

Average recoveries for internal standards ranged 48-113% and their ranges for the samples

155

and blanks are presented in SI, Table S2.

156

Field (N=4), transport (N=4) and laboratory method (N=3blanks were extracted and analyzed

157

along with samples to reveal any contamination during handling, transport and laboratory

158

preparations. Field blanks are defined as PUFs that have been assembled in PAS and then

159

immediately disassembled in the field; transport blanks are PUFs which were never exposed

160

in the field; and laboratory method blanks are simply clean PUFs. The ranges of blank

161

amounts are presented in SI, Table S3. Method detection limits (MDLs) were determined for

162

each compound from average blank amounts plus three times the standard deviation of these

163

amounts. When the target compound was not identified in the blanks, an instrumental

164

detection limit (signal/noise 3:1) was used to estimate a MDL value.

165

Parallel samplers were deployed at two sampling sites. Between parallels, the relative

166

standard deviations were 0.1-27% for PCBs, 7.8-21% for PBDEs, 2.6-28% PAHs, 3-39% for

167

HCHs, 4-34 for p,p’-DDT, 4-28% for HCB, 6% for SCCPs, 0-4% for chlordanes. The average

168

value of the parallel samples represented sample results at these sites.

169 8 ACS Paragon Plus Environment

Page 9 of 36

Environmental Science & Technology

170

Estimation of concentrations in air

171

A sampling volume estimate is needed to calculate concentrations in air from the measured

172

amounts of POPs in the PAS. Still, the most appropriate approach for back-calculation of

173

concentrations in air from PAS sampling is currently debated and sample volume estimations

174

do include uncertainties.31-34 In the current study, a range for the estimated sampling volume

175

was obtained for each compound as proposed by Harner et al.35 The estimation is based on

176

duration of exposure, average air temperature, PUF characteristics, compound-specific KOA-

177

values and assumptions of sampling rates and particle fractions (see further details in the SI,

178

Table S5).

179

180

Data treatment and analysis

181

All 23 sites were included in the data analysis. Statistical analysis was executed using R,

182

ver.3.1.1., and statistical significance was defined as p < 0.05. When summed amounts were

183

calculated for POP groups, MDL/√2 was used for sample amounts that were lower than the

184

MDL. Summary statistics for compounds with detection frequencies between 20% and 80%

185

were calculated using the Kaplan-Meier method with the NADA package for R according to

186

Helsel (2005). Correlations between components are presented as Spearman`s rank

187

correlations. Spatial presentation of the data was performed with the ggplot2 and ggmap

188

packages in R, in which the background maps are provided by Google Inc. Due to

189

uncertainties in back-calculated concentrations in air, spatial patterns are interpreted on the

190

basis of measured amounts. Principal component analyses (PCA) were performed with the

191

ggbiplot package in R on the compounds presented in SI, Table S3 (SCCPs were excluded

192

due to missing values).

193 9 ACS Paragon Plus Environment

Environmental Science & Technology

Page 10 of 36

194

Estimations of human health risks from inhalation exposure

195

Toxic equivalent quotients (TEQs) were calculated based on toxic equivalency factors (TEFs)

196

for PAHs36 (fluorene=0.001, phenanthrene=0.001, anthracene=0.01, fluoranthene=0.001,

197

pyrene=0.001, benz(a)anthracene=0.1, chrysene/triphenylene=0.01, benzo(a)pyrene=1) and

198

PCBs37 (PCB-118=0.000033), as well as the PUF-derived concentrations in air for each site.

10 ACS Paragon Plus Environment

Page 11 of 36

Environmental Science & Technology

199

Results and discussion

200

Results summary

201

The measured amounts were highest for PAHs and SCCPs whereas PCBs, DDTs, chlordanes,

202

HCB and PBDEs were several orders of magnitude lower in comparison. The correlations

203

between compounds within each of the PAH and PCB groups were strong (most Spearman`s

204

rho >0.8), whereas correlations were weaker, or not significant, for PBDEs and pesticides (SI,

205

Table S4).

206

The levels for Σ7PCBs were highest at three sampling sites located close to ship breaking

207

activities and especially at one site where measured amounts were 19 times higher than the

208

median of Σ7PCBs (Figure 1B). Still, the amounts of Σ7PCBs at the other sampling sites were

209

also considerable (Figure 1A). The lower-chlorinated PCB congeners contributed most to the

210

Σ7PCBs (34%, 27%, and 15% of Σ7PCBs for PCB-28, -52, -101, respectively; SI, Table S3).

211

The levels of PBDEs were low and results are only presented for PBDE-47 and -99 due to

212

quality control measures and limitations of the sampling method. The highest amounts of the

213

two PBDE congeners were found at sites in the city center.

214

The sites with the highest levels of Σ8PAHs (Figure 1C) paralleled those of the PCBs and

215

there was moderate correlation of many PAHs with PCBs (Spearman`s rho>0.3; SI, Table

216

S4). Phenanthrene (46%), fluoranthene (18%), fluorene (17%), pyrene (14%) contributed

217

most to the median Σ8PAHs.

218

The highest measured amounts of HCB was found at one site in the vicinity of ship breaking

219

activities (Figure 1D) which was same site that had the extreme values for Σ7PCBs and

220

Σ8PAHs. However, HCB levels were high also at other sites in the ship breaking area and in

221

the city.

11 ACS Paragon Plus Environment

Environmental Science & Technology

Page 12 of 36

222

The most abundant pesticides found in the study were DDT and DDE. The highest levels of

223

p,p’-DDT (Figure 1E) and o,p’-DDT (data not shown) were found at sites in urban areas. The

224

spatial trends for HCHs diverged between the three isomers measured (SI, Figure S3). Levels

225

of α-HCH were highest at the urban sites, whereas β-HCH levels were highest at one site near

226

ship breaking activities as well as at numerous urban sites. Levels of γ-HCH were highest at

227

sites close to ship breaking activities. Sample amounts of chlordanes were low and spatial

228

patterns (presented for trans-chlordane in SI, Figure S3) resembled those for γ-HCH.

229

The highest levels of SCCPs were found in the urban area (Figure 1F) and there appeared to

230

be a declining trend of these levels with increasing distance from the city center. SCCP results

231

for the site closest to ship breaking activities that was highest for PCBs and PAHs was

232

unfortunately not available as this sample was damaged during laboratory analyses.

233

234

Interpretation of PAH molecular ratios

235

Molecular diagnostic ratios (MDRs) are ratios between certain PAHs which can indicate

236

characteristics related to their emission sources.38-40 Sampling performed in narrow time spans

237

across limited geographical areas close to suspected sources has been suggested to facilitate

238

interpretation of MDRs and renders the present study interesting in this context. Three MDRs

239

were calculated based on PAHs with high analytical detection (Figure 2). The ratios of

240

anthracene/anthracene + phenanthrene (ANT/(ANT + PHE)) and

241

benz(a)anthracene/benz(a)anthracene + chrysene (BaA/(BaA + CHR)) were significantly

242

different between site classifications (5 classes, see SI, Table S1; Kruskal-Wallis test, p=0.004

243

for both group tests). It should be noted that quantified amounts of chrysene include

244

uncertainties due to analytical co-elution with triphenylene. The third MDR representing

12 ACS Paragon Plus Environment

Page 13 of 36

Environmental Science & Technology

245

fluoranthene/fluoranthene + pyrene (FLT/(FLT + PYR)) was not significantly different across

246

classes (Kruskal-Wallis test, p>0.05).

247

MDR values above given cut off values indicate combustion of grass and wood rather than

248

fossil fuel as sources to PAHs.39, 40 Ratios were above the respective cut off values at four

249

sites for ANT/(ANT + PHE) and at six sites for BaA/(BaA + CHR) in the ship breaking area.

250

In addition, ratios were above the respective cut off values at three sites for BaA/(BaA +

251

CHR) that were classified as industrial or affected by traffic within the city. Together, MDR

252

values were high at sites near ship breaking activities and at some industrial sites which

253

suggest that PAHs originate from combustion processes at these sites. The FLT/(FLT + PYR)

254

ratio was above the cut off value at all sites which could be indicative of widespread

255

combustion of wood and grass, etc. Compared to coastal, urban and agricultural sites in

256

Southern India, ratio values for BaA/(BaA + CHR) were higher at the sites close to ship

257

breaking activities in Chittagong and FLT/(FLT + PYR) values were in the same range.41

258

259

Methodological limitations

260

PUF-based PAS was selected as sampling material based on their performance in spatial

261

mapping on both a regional and global scale (see references in method section). However,

262

employing PUF-based PAS as sampling method of relatively volatile substances has both

263

advantages and draw-backs.32 In order to focus the discussion and avoid artifacts due to

264

choice of sampling method, the presented results have been limited to compounds in a

265

selected range of KOA-values (SI, Table S3; ranging 6.21 - 11.38 at 24°C which was the

266

average estimated temperature for the sampling period). An additional limitation is that the

267

sampling could be influenced by high amounts of ambient particles as well as the fact that

268

there was no precipitation to settle the particles during the sampling period.29 In addition to 13 ACS Paragon Plus Environment

Environmental Science & Technology

Page 14 of 36

269

particle impaction, the high temperatures found during the sampling period may have

270

enhanced the uptake of both the gas phase and the particle bound phase of POPs during

271

deployment.22 There is likely some variation in particular concentrations and temperatures

272

within the study area that might have affected the contaminant uptake at some sampling sites,

273

but the spatial comparisons are still considered valid. Overall, the sampling period provides a

274

temporal snap shot in the area both with regards to seasonal variability related to changing

275

intensities of ship breaking and industrial activities. There was no apparent trend with height

276

of sampler position above sea level.

277

PUF-derived concentrations in air are presented even though they include uncertainties as

278

exact normalization to measured sampling volumes was not possible. Therefore, a range of

279

sampling volumes was estimated for each compound based on ranges in temperatures and

280

theoretical ranges in ambient particle-fractions during the sampling according to Harner et

281

al.35 As the sampling rates vary by uptake phases, gas-particle partitioning, wind speed and

282

temperature,32 the estimates may appear crude, however, we have employed a compound-

283

specific strategy to take account of the KOA-specific variation in sampling volumes.

284

285

Local emission sources of POPs

286

This study presents ambient air data across an area that covers residential, industrial and ship

287

breaking areas as well as sites that can be considered background sites. Poor air quality is an

288

identified problem in several areas of Bangladesh, also in Chittagong.29, 42, 43 However, to the

289

extent of our knowledge no previous survey of POP concentrations in ambient air has been

290

performed in Bangladesh. The results of the present study demonstrate high measured

291

amounts of various POPs considering the short sampling period. Furthermore, the

292

discrepancies in spatial patterns for PCBs, HCB, and PAHs as compared to DDTs and HCHs 14 ACS Paragon Plus Environment

Page 15 of 36

Environmental Science & Technology

293

indicate different emission sources for the different compound classes. Specifically, the

294

results indicate that ship breaking activities can be important potential local emission sources

295

of PCBs, PAHs and HCB. Furthermore, sites in urban areas appeared to be especially

296

influenced by sources of DDTs and SCCPs. Together, these results add to the emphasis on

297

challenges related to atmospheric pollution in Chittagong.

298

The PCA analyses demonstrated that the main variation in the sample set is related to the

299

samples collected close to ship breaking activities and that the other site classes (industrial,

300

traffic-influenced, residential, background) are distinguished from these samples (SI, Figure

301

S4). Overall, the PAHs, PCBs and HCB were clustered together along the first factor away

302

from o,p’-DDT and α-HCH which agrees with the spatial trends of these compounds

303

(displayed in Figures 1 and S3). The joint interpretation of spatial patterns in concentration

304

trends, PAH MDRs, compound correlations and PCA patterns has provided indications of

305

potential emission sources for the different contaminants. Overall, our results are in

306

accordance with previously suggested potential emission sources such as release and/or

307

production of contaminants related to ship breaking and industrial activities, as well as

308

influence of stockpiles of pesticides or PCBs.4

309

-

Ship breaking activities

310

The levels of PCBs, PAHs and HCB were high at sites close to the beach and the spatial

311

trends for these compounds indicate the role of ship structures and their dismantling processes

312

as potential local emission sources of these compounds. Many registered activities in this area

313

are designated as iron and steel manufacture, re-rolling mills, and simply as ship breaking.

314

The spatial trends for PCBs, PAHs and HCB and their inter-correlations indicate common

315

emissions of these compounds which could be related to release and/or formation through

316

combustion processes as burning of scrap materials is common in the ship breaking areas.12

15 ACS Paragon Plus Environment

Environmental Science & Technology

Page 16 of 36

317

This is further supported by the high MDR ratios indicative of combustion of wood and

318

grass42 at sampling sites classified as influenced by ship breaking. Ships may contain PCBs in

319

WEEE (e.g. transformers and capacitors) and paints.3, 15 Furthermore, PCBs, PAHs and HCB

320

could be generated and/or released during combustion through burning of scrap and organic

321

materials from the ships.17-19 The elevated levels of the same POPs at urban sites could also be

322

related to ship breaking activities as there is subsequent processing and treatment of materials

323

from the ships in Chittagong city.12, 29 Based on prevailing winds, the urban areas are

324

downwind from the ship breaking sites and transport by air can also havecontributed to the

325

sample amounts at sampling sites in the urban areas.

326

-

Industrial sites

327

The sampling campaign was conducted in the dry season which is when the most intense

328

emission sources are active in Bangladesh. The sources include industrial activities, brick

329

kilns, wood burning, metal smelters, road dust, motor vehicles, soil dust, and sea salt – which

330

have all been identified as important sources to particulate pollution.29, 42, 43 As the sampling

331

campaign was conducted during a period in which industrial activity and particle fractions in

332

the air was generally high,29 the sample amounts of PAHs, PCBs and HCB may also reflect

333

sampling of target analytes sorbed onto particles.32 A study describing a sampling campaign

334

conducted in parallel to the present study has reported concentrations of NO2 and SO2 in

335

ambient air. Their spatial distributions were largely in accordance with recognized industrial

336

activities and traffic, respectively, but did not display high concentrations at sites near ship

337

breaking activities.29 Spatial patterns within the urban areas for POP concentrations that could

338

be related to industrial activities crudely correspond with those of NO2 and SO2

339

concentrations; this only adds support to the interpretation of the industrial activities as

340

contributing emission sources to PAHs, PCBs and HCB in ambient air in the city.

341

Accordingly, contributions from various industrial activities have been shown to contribute to 16 ACS Paragon Plus Environment

Page 17 of 36

Environmental Science & Technology

342

the ambient air loading of PCBs20 and could contribute to the spatial patterns of PCBs in

343

urban air in Chittagong (Figure 1A).

344

-

Waste sites

345

Burning of waste at waste dump sites is common in Bangladesh3 and these combustion

346

processes can release PAHs, PCBs and HCB.18, 19 There are waste sites in the urban areas

347

which also could be contributing to the high measurements at urban sample sites (Figure 1A-

348

D). As mentioned, further processing of materials from ships could result in waste in urban

349

areas3, 29 thereby also contribute to emissions to ambient air at those sites.

350

-

Stockpiles and use of pesticides

351

The spatial trends for DDTs indicated emission sources in urban areas which could be

352

explained by historic production of DDT in the Chittagong area as well as stockpiles and

353

continued illegal use.3, 4 The median p,p’-DDT/ p,p’-DDE ratio was 1.92 (ranging 0.87 –

354

2.82) and the median o,p’-DDT/ p,p’-DDT ratio was 0.48 (ranging 0.30-0.84). The high p,p’-

355

DDT/ p,p’-DDE ratios at some sites indicate that the emissions of DDT at these sites are

356

recent.44 Also, the ratio is higher at some urban sites in Chittagong compared to other

357

contemporary studies in Asia45, 46 and Europe.27 The low o,p’-DDT/ p,p’-DDT ratios indicate

358

that sources to DDT were technical DDT (ratio >1)47 usage which has

359

been reported in other studies from Asia.45, 46, 48, 49 Together, these results support that there is

360

recent use and/or emissions from stockpiles of DDT in the Chittagong area.

361

For the sum of HCHs, the median contribution from each isomer was 42%, 4%, and 54% for

362

α-, β-, and γ-HCH, respectively. Similar contributions of both α- and γ- HCH to the sum HCH

363

implies emissions of both technical HCH (α-HCH: 55-80%; β-HCH: 5-14%; γ-HCH 8-15%)

364

and lindane (>90% γ-HCH).50 There were considerable amounts of γ-HCH found at the same

365

sites that also contained the extremes for PCBs, PAHs and HCBs at the sites near ship 17 ACS Paragon Plus Environment

Environmental Science & Technology

366

breaking activities. This could indicate their common release and/or signatures of continued

367

or historic use of lindane at that site.

368

-

Page 18 of 36

Sources of SCCPs

369

The spatial pattern of SCCPs shows elevated concentrations in the city (Figure 1F). This

370

suggests that the main emission sources may be located within the urban areas. SCCPs are

371

known to be found in metal-working lubricants, sealants, plasticizers, and flame retardants.21

372

It is plausible that these usages may represent potential sources in Chittagong as well. SCCPs

373

were in the same orders of magnitude as the PAHs, which shows that these compounds are

374

abundant in air in the Chittagong area.

375

376

Human health risk assessment

377

TEQ values based on PAHs and PCB-118 (ranging 0.39-40 ng TEQ/m3; SI, Table S5) were

378

largely dominated by PAHs and above the carcinogenic risk limit (TEQ of >1 ng TEQ/m3)51

379

at 18 of the sites. This indicates that PAH exposure through inhalation cannot be considered

380

safe at several sites and could involve elevated health risks. The highest value for TEQ was

381

found at the site with the highest concentrations in the ship breaking area (SI, Figure S5). It

382

should be noted that the calculations: i) were based on a limited number of PAHs and only

383

one PCB; and ii), incorporate the uncertainties of the PUF-derived concentrations in air. Still,

384

the relatively large exceedance of the threshold found at some sites indicate that further

385

studies should address the health risks for humans in the areas with the highest concentrations

386

of contaminants, with special consideration for the workers involved in the ship breaking

387

activities. Possible exceedance of international standards and guideline values for health

388

related to concentrations of SO2 and NO2 in ambient air has also been reported in this area.29

389

The highest values in this study is higher than those reported in southern India where PAH18 ACS Paragon Plus Environment

Page 19 of 36

Environmental Science & Technology

390

TEQs only exceeded the TEQ threshold in the summer months.41 As this study was performed

391

in the season during the most intense industrial activities, levels of PAHs and PCBs could be

392

lower during the wet season which also has less intense industrial activity. A follow-up study

393

should therefore be performed to assess the seasonal variability of POPs in ambient air in

394

Chittagong.

395

Ship breaking activities in Bangladesh employ over 100,000 workers and an estimated 50,000

396

children are involved in informal e-waste recycling of which 40% takes place in ship breaking

397

yards.5 Detrimental health effects have been emphasized following occupational exposure

398

related to informal recycling processes of obsolete ships12, 52, 53 and e-waste.54-56 There are

399

considerable health hazards for workers within ship breaking that are related to accidents in

400

addition to the chemical exposures from asbestos, heavy metals and POPs.12, 57 Furthermore,

401

significant correlations between concentrations of various POPs in air (including, PCBs,

402

pesticides and PBDEs) and human serum have been reported in China which emphasizes the

403

relevance also of inhalation as exposure pathway in areas with considerable pollution.58 Thus,

404

the concentrations of POPs in ambient air in Chittagong could be detrimental to human health

405

and add to the health hazards related to ship breaking activities.

406

407

Comparisons with other studies

408

Among the PAHs included in this study, phenanthrene was the most prevalent compound.

409

This has also previously been observed in studies of background air performed in both Asia

410

(India and South Korea),41, 59 and Europe.27 However, the estimated median and maximum

411

concentrations of phenanthrene in this study were up to orders of magnitude higher than in the

412

studies referred to above. Furthermore, the concentrations of phenanthrene in this study was

413

also higher than those in ambient air in Shanghai, China,60 and at industrial sites in Taiwan.61 19 ACS Paragon Plus Environment

Environmental Science & Technology

Page 20 of 36

414

The estimated concentrations of Σ7PCBs in air at sites close to ship breaking activities were

415

within the range of other contemporary monitoring results in Southeast Asian areas influenced

416

by informal e-waste treatment17, 62 or where e-waste treatment has been suggested to

417

contribute to high concentrations63, 64 (Figure 3). The median concentration of Σ7PCBs in air

418

in Chittagong was comparable to those in large Asian cities45, 62, 64, 65 but higher than

419

European background sites.27 The PCB congener profile in air in Chittagong displayed less

420

PCB-28 relative to the higher chlorinated congeners compared to that observed in multi-site

421

studies in India and China49, 66 but was similar to that reported in multi-site studies in

422

Europe.23, 27 In comparison to atmospheric PCB profiles resulting from industrial thermal

423

processes, the observed contributions from PCB-28 were low, and can be considered similar

424

to those for secondary copper or zinc smelting.20 This result could be in agreement with the

425

ship breaking and metal re-rolling activities in the area.

426

The current concentrations of DDT are within the ranges of those found in ambient air in

427

India.49 DDT is still actively used in India, which adds further support to the hypothesis of

428

ongoing use of DDT in Chittagong. The concentrations of DDT were in the high range

429

compared to other studies in China, Japan, South Korea and Europe.27, 48

430

Concentrations of HCB in Chittagong were also in the high range in comparison to

431

concentrations found in the same studies mentioned above.27, 48

432

Estimations of sampling volumes are not presented for SCCPs by Harner et al.,35 but

433

assuming a sampling rate of 4.2 m3/day67 for 8 days, the median concentration of SCCPs is 46

434

ng/m3 which is several fold higher than concentrations reported in India and Pakistan

435

(sampled in 2006 and 2011, mean 8.11 ng/m3, ranging